This Talk

• How does a change in pronunciation propogate across a speech community?
• When a pronunciation changes over time, what aspect of speakers’ knowledge of their language is changing?
• What aspects of speakers’ cognition constrain a pronunciation change like this in the first place?

The Philadelphia Neighborhood Corpus

The Philadelphia Neighborhood Corpus

• Despite having such a long time domain, the PNC doesn’t quite directly observe the propogation of a pronunciation change across a speech community. We’ll still try to make some reasonable inferences on the basis of the data that we do have.

The Data

library(shiny)
runApp(system.file("appdir/means", package="phoneticChange"))

General pattern

What does it Mean

Population Shift?

What would it look like?

Population Shift

• Speakers are not internally variable. You are either a raising speaker, or a non-raising speaker.
• The speech community is highly variable.

What does it mean?

Lexicon

What would it look like?

Lexicon

• Speakers are internally variable. Sometimes they’ll say a raising word, and other times they’ll say a non-raising word.
• The speech communuty isn’t very variable. Speakers should be more or less similar to eachother.

What does it mean?

Variable Rule

• /ay/ = [+low]
• with probability \(p\), ay \(\rightarrow\) [-low]/__[-voice]
  • beginning of the change, \(p=0\)
  • middle of the change, \(p=0.5\)
  • end of the change, \(p=1\)

What does it mean?

Variable Rule

What would it look like?

Variable Rule

• Speakers would be internally variable, alternatively raising and not raising /ay/ with some internally consistant probability.
• The speech communuty wouldn’t be very variable. There would be some characteristic probability of raising for birth cohorts & social strata.

What does it mean?

Continuous Change

What would it look like?

Continuous Change

• Speakers wouldn’t be very variable aside from the intrinsic variation involved in trying to hit a real-valued target.
• The speech community wouldn’t very variable. There would be some characteristic pronunciation target for birth cohorts & social strata.

Totally No Stawmen Here

• There are at least a handfull of examples of language change that did progress like each of the models described here.
• But some theories of phonology, phonetics, and sound change do rule out the possibility of the final, continuous change model.
• The first three models seem to be the ones most commonly assumed by new entrants to the field.
• There is often covert variation between practitioners as to which model they’re assuming!

Trend with speaker means

Cohen’s D

What it means

• We can rule out the population shift model.
• The lexicon shift model, and the variable rule models can’t be ruled out yet.
  • If speakers were sampling from two distributions, or two lexicons, their means would still shift continuously.

Distributional Properties

• Both the kurtosis and the standard deviation of a mixture distribution should systematically co-vary with the mean.

library(shiny)
runApp(system.file("appdir/mixdists", package="phoneticChange"))

Distributional Properties

Distributional Properties

Distributional Properties

Simulation

Distributional Properties

Simulation

Distributional Properties

Simulation

Distributional Properties

Simulation

Distributional Properties

Comparsion to non-change

Distributional Properties

Comparsion to non-change

Distributional Properties

• It doesn’t look like any of the categorical mixing models characterize the data well.
  • Looking just at the distributional properties of pre-voiceless /ay/, it doesn’t look like speakers are every sampling from two different distributions.
  • Comparing pre-voiceless /ay/ to the rest of /ay/, its distributional properties aren’t different, or at least not in the way expected.

• The continuous shift model looks like it best characterizes the data.

Where is this change?

• Is this change being mostly driven by individual speakers changing how they speak?
• Or is it being driven by inter-generational shift?

Problem

• The PNC has no longitudinal data for individual speakers.

Where is this change?

Problem

Where is this change?

  ays_means %>% 
    filter(plt_vclass == "ay0") %>%
    gam(F1_n ~ ti(age) + ti(DOB) + ti(age, DOB), data = .) -> model

Where is this change?

Where is this change?

Where is this change?

Where is this change?

• The estimated age trends within birth cohorts seem relatively flat.
• The change seems to mostly play out between generational cohorts.

Non-random errors in the signal

Ohala (1981)

Non-random errors in the signal

Pre-voiceless Shortening

• Before voiceless consonants, vowels are shorter.
• With less time to make such a big gesture for /ay/, speakers cut corners and pronounce the first part higher.

Offglide Peripheralizatiom

• Before voiceless consonants, the [i] part of /ay/ is pronounced even higher and fronter than usual.

Non-random errors in the signal

A natural experiment

The difference between /t/ and /d/ is largely neutralized in certain contexts.

Flapping Neutralization

Flapping Neutralization

Flapping Neutralization

Flapping Neutralization

• The non-random errors in the noise seem to be distributed differently between pre-faithful and pre-flapped contexts:
  • Duration: faithful and flapped /t/ > flapped /d/ > faithful /d/
  • Peripheralization: faithful /t/ > flapped /t/ and faithful and flapped /d/

The Change

The Change

• The degree of participation in the change appears not to be circumscribed by other continuous parameters of speech, by other, top-down cognitive factors.

Non-linear Bayesian Modelling

Non-linear Bayesian Modelling

Non-linear Bayesian Modelling

Other Things I’ve Looked At

• Word Frequency
• Ratio with which a stem appears in a flapping vs a faithful context

Conclusions

• It is possible for continuous properites of speech to change.
  • These continuous properties must be part of speakers’ knoweldge of their language.
• These changes are not necessarilly circumscribed by other continuous properties of speech.
  • A top down, categorical aspect of speakers’ knowledge of their language appears to have played a crucial role at the initiation of this sound change.
• There is still a lot of work to be done in understanding how and why changes like this happen, if our reasonable assumptions about them don’t seem to pan out.